Recent success in the prevention of prematurity in a high-risk population by the use of the long-acting progestational agent 17 alpha hydroxyprogesterone caproate (17 alpha OHP-C) suggests that hormonal abnormalities constitute a major etiologic factor in premature labor. Selected hormonal studies in a high-risk population are underway in an effort to identify the specific abnormalities and thereby improve the diagnosis and treatment of impending premature labor. The specific aims of this project are to determine the sequential changes in maternal plasma hormonal levels of progesterone, 17-beta estradiol, dehydroisoandrosterone sulfate, cortisol, prostaglandins and 17 alpha OHP-C and 24-hour urine catecholamine levels in: a) normal patients carrying their pregnancies to term (controls); b) high-risk patients delivering prematurely and c) high-risk patients treated with 17 alpha OHP-C during the course of their pregnancies. By comparing differences in hormonal values at varying weeks of pregnancy and prior to the onset of labor, we hope to determine the hormonal changes preceding the onset of premature and spontaneous labor. By determining the changes in plasma hormonal levels associated with the administration of 17 alpha OHP-C, we hope to determine the modus operandi of this hormone and the dose-response ratios in specific patients.